Automatic circuit breaker with calibration provisions



March 5, 1957 P. M. CHRISTENSEN 2,784,278

AUTOMATIC CIRCUIT BREAKER WITH CALIBRATION PROVISIONS Filed Feb. 1, 1954 8 INVEN TOR.

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ATTORNEYS United States Patent AUTOMATIC CIRCUIT BREAKER WITH CALIBRATION PROVISIONS Paul M. Christensen, West Orange, N. J., assignor to Federal Electric Products Company, Newark, N. J., a corporation of Delaware Application February 1, 1954, Serial No. 407,364 18 Claims. (Cl. 200-116) 'The present invention relates to automatic circuit breakers of the general type disclosed in United States patents numbered 2,209,319, 2,642,509, 2,647,186 and 2,647,187, all of which are assigned to the assignee hereof, and in the U. S. patent application of Alexander R. Norden Serial No. 369,366, filed July 21, 1953, and assigned to the assignee hereof, and in particular, to calibrating provision for the circuit breakers.

In circuit breakers of the general type to which the present invention relates, provision is made for a movable contact or switch member which bodily mounts currentresponsive latching means, including a flexible latching element, and which pivotally carries an actuating element, the latter being operatively connected to the movable contact member through a releasable engagement with the latching element, for manually operating the circuit breaker to open and closed positions thereof. The current time rating for the circuit breaker is dependent upon the degree or extent of overlap of the actuator and the latching element at said releasable connection thereof. In order to calibrate the circuit breaker for a predetermined current-time rating, the releasable connection of the actuator and the latching element is adjusted by varying the degree or extent of overlap thereof. In each of the previously mentioned patents, provision is made for adjusting said releasable connection in a single sense or direction, and in the previously mentioned application, provision is made for adjusting said releasable connection in opposite senses or directions so as to compensate for or to neutralize overcaiibration. In said patents, the calibration provision is constituted by an opening formed in the movable contact member, which opening is adapted to receive a tapered element for displacing a part of the movable contact member, said displaced part mounting the flexible latching element, as in Patent No. 2,209,319 or said displaced part mounting the actuating element as in said other patents. in said copending application, the openings are provided in opposite portions of the movable contact member so as to provide for calibration in opposite senses or directions.

In view of the foregoing, and as the primary object of the present invention, calibration in opposite senses or directions may be accomplished through the utilization of a tapered element and without the necessity of 7 providing the additional calibration opening.

Another object is the provision of a circuit breaker construction wherein a calibrating element or tool may be operated in opposite directions, at one position thereof, for effecting calibration in opposite directions or senses.

A further object is the provision of a circuit breaker construction having a generally improved and simplified calibration provision.

The above and other objects, features and advantages of the present invention will be more fully understood from the following description considered in connection with the accompanying illustrative drawings.

'ice

in the drawings:

Fig. 1 is a side view of a circuit breaker, pursuant to the present invention, and illustrates the best mode presently contemplated of carrying out the invention, a part of the casing being removed and the breaker being illustrated in the circuit closed condition thereof;

Fig. 2 is a sectional view, on an enlarged scale, taken on the line 22 of Fig. 1;

Fig. 3 is a view similar to Fig. 2 and illustrates a modification;

Fig. 4 is a fragmentary view similar to Fig. 1 and illustrates another embodiment of the invention;

Fig. 5 is a sectional view, on an enlarged scale, taken on the line 5-5 of Fig. 4;

Fig. 6 is a fragmentary view similar to Fig. l and illustrates a further embodiment of the invention;

Fig. 7 is a sectional view on an enlarged scale, taken on the line 77 of Fig. 6; and

Fig. 8 is a fragmentary view of a portion of the circuit breaker mechanism, as in Fig. 1, and illustrates adjusted or calibrated positions thereof.

In general, the circuit breakers illustrated herein, and in the previously mentioned patents and application, each comprises a movable contact member 10 which carries a movable contact 12 for engagement with and disengagement from a companion stationary contact 14. Said movable contact member is provided with a pivotally mounted actuator 16 which is releasably latched to said movable contact member by means of a current-responsive or other overload device 18. As here shown, the device 18 is constituted by a flexible bimetallic member which is carried by the movable contact member 10 and has a free end portion 20 which releasably engages said actuator under normal load conditions so as to enable the movable contact member to be held in circuit closed position, or to be manually operated to and from said position by means of the handle 22. Upon release of said actuator by said device, there results the movement of said movable contact member automatically to its open circuit position by means of the compression spring 24 which is interposed between the contact member 10 and the handle 22, as fully illustrated and described in said Patent 2,647,186.

Referring now to Figs. 1 and 2 in detail, which represent the presently preferred embodiment of the invention, there is illustrated the circuit breaker 30 provided with the previously described operating mechanism which is generally indicated by the reference numeral 32. As here shown, the circuit breaker mechanism is provided within a casing or housing constituted by the companion casing members 34 and 36, molded of suitable insulation material, and retained in housing defining relation, as by the securing elements 38. The contact member 10 is mounted for pivotal movement in substantially the same manner as in the previously mentioned Patent No. 2,642,509. More specifically, the movable contact member is provided with a generally circular opening 40 at the axis about which it pivotally moves. An opening 42 formed in the lower marginal edge of the contact member 10 constitutes an interruption in the periphery of said contact member and extends to the circular aperture 40. It will be noted that the opening 42 is formed in the narrower portion 44 of the movable contact member, on the free end of which portion the actuator 16 is pivotally mounted. The body portion 46 of the movable contact member forms the wider and generally larger portion thereof and extends to the left, viewing Fig. 1, of the circular aperture 40 through which the pivot axis of the movable contact member extends.

In order to provide for both the pivotal mounting and the calibration of the movable contact member 10, there is provided a calibrating element or spindle 48 of the a atars type illustrated and described in Patent 2,642,509. Said spindle is provided with a screw driver slot 50, at one end thereof, and the other end is provided with a threaded portion 52 which is threadedly engaged in an internally screw-threaded nut 54. Said nut has at one end thereof, a cylindrical collar 56 of reduced diameter, which collar has rotary bearing support in the bearing aperture 58 provided in the casing member 34. In order to prevent relative movement between the nut 54 and the movable contact 10, the latter is provided with a pre erably pressed out part so which engages in a cut out 62 formed in the flange 70 provided at the other end of the nut. Intermediate the ends thereof, the pin member 48 is provided with a tapered portion 64. The casing part 36 is provided with the portion as which serves as a bearing support for the bearing portion 68 of the spindle s. Therefore, it will be apparent that when the spindle 43 is disposed within the .casing, as illustrated in Fig. 2, said spindle will serve as the'pivot for the movable contact member 14}, in view of the fact that the nut 54'does not rotate relative to the movable member, as previously described. 7

If the calibrating member or spindle 48 is rotated in a direction to thread the threaded end '2 thereof further into the threaded nut 54, so that the spindle moves axially thereof in the direction of the arrow 72 in Fig. 2, and transversely of the plane of the movable contact member, it will be apparent that the axially tapering portion 64 thereof will be progressively moved into the aperture 4-6 in the movable contact member. As said tapering portion advances into the moves through the aperture 4%, the latter is distended and the narrower portion 44 of the movable contact member is displaced in the plane thereof from the wider body part 46. This action is due to the fact that the distension of aperture it? causes the distention of the aperture 42 which extends through the movable Contact member from the aperture 4% therein to the marginal edge thereof.

Referring now to Fig. 8, the broken line position of the movable contact member it? indicates a position for maximum overlap of the tip 74 of the actuator relative to th free end 20 of the bimetallic latch 18. As the pin member 48 is threaded into the movable contact member 10 so that the pin member moves in the direction of the arrow 72 in Fig. 2, the sides of the aperture 532 are forced apart, the relative displacement of said opposing sides resulting from full entry of the tapering portion 64 into the aperture 4t? being illustrated in fill l ne in Figure 8. It will be apparent that as a result of said distention or displacement of the opposing sides of the aperture 4-2, the entire narrower portion 44 of the movable contact member 1%} is moved in a plane thereof from the broken line position thereof to the full line position thereof, thereby moving the actuator 16 relative to the bimetal 13 to reduce the degree of over.- lap, as illustrated in said figure. The relative move.- rnent of the actuator 16 and the bimetal 18 in said direction, namely to reduce the degree of overlap thereof, calibrates the circuit breaker in a direction to reduce the current rating thereof since a smaller degree of deflection is now required of the control element 18 in the direction of the arrow 76 in Fig. 8 to effect the tripping of the circuit breaker.

However, in the event that the movable element 48 has been moved in tr c direction of the arrow 72 for a greater extent than is desired, it will be apparent that the circuit breaker mechanism may be overcalibrated so as to have a lower current rating than is required or desired for a particular application. Pursuant to the present invention, provision is made for calibrating in the opposite direction so that the movable contact member portion 44 can move in a direction from its full line position in Fig. 8 toward its broken line position, to compensate for or to neutralize the described overcalibration. This is accomplished by providing the movable contact member 10 witha resilient characteristic so that it can spring back in a direction from the full line position thereof toward the broken line position thereof, illustrated in Fig. 8, to the extent or degree which may be required to compensate for the overcalibration. More specifically, this is accomplished by forming the movable contact member 10 of a metal having sufficient resiliency so that overcalibration can be neutralized by a reverse movement of the tapered spindle 45 in which the latter moves in a direction opposite the arrow 72 to permit for the contraction of the apertures 4i and 42.

In the foregoing connection, the movable contact member 10 may be formed preferably of beryllium copper or Phosphor bronze to provide the required resiliency. However, it will be understood that other suitable ma terials, which have sulficient resiliency to spring back after distortion or displacement of portions thereof may be used in place of the materials specifically set forth, by way of example, herein. In view therefore of the resilient character of the material of which the movable contact member 10 is formed, pursuant to the present invention, it will be apparent that if the calibration ele ment 48 is moved in the direction of the arrow 72 for a greater extent than is desired, and therefore produces overcalibration in the direction of a reduced current rating or current response for the circuit breaker, it is then necessary only to rotate the calibrating member 4-8 in the opposite direction so as to axially move the latter in a direction opposite the arrow 72. Consequently it will be apparent that as the tapered portion 64 is withdrawn from the aperture 40, and due to the inherent resiliency of the material from which the movable contact member 16 is formed, the opposing sides of the aperture 42 at the marginal edge of the movable contact member, as well as the wall of the aperture 46, will move together from their distended conditions, and consequently the displaced portion 44 of the movable contactmember will move, in the plane thereof, in the general direction from the full line position thereof illustrated in Fig. 8 to the broken line position thereof. This will increase the degree or extent of overlap of the tip 74 of the actuator 16 relative to the free end 20 of the flexible control member 18 to calibrate in the opposite sense for increased current rating to neutralize the overcalibration in the direction of decreased current rating. The degree of neutralization is controlled by the extent to which the spindle is withdrawn from the movable contact member.

In view of the foregoing, it will therefore be readily apparent that the inward movement of the calibrating member or spindle 48 relative to and transversely of the movable contact member It) results in calibration in a first direction or sense to reduce the current rating or response of the circuit breaker, and the outward movement of the calibrating element 48, in the opposite direction, permits the movable contact member in, due to its inherent resiliency, to spring back toward its original condition so as to calibrate in an opposite direction or sense, namely in a direction to increase the current rating or response of the circuit breaker.

It will be noted that the described calibration of the circuit breaker 30 in opposite senses or directions may be achieved without removing the circuit breaker mechanism 32 from the casing or housing. In this connection, it will be noted that the casing part 36 is apertured as at '78 to expose the slotted head of the calibrating element 48, so that a screwdriver or other suitable tool may be inserted through the opening 78 to effect the calibration of the circuit breaker. After the circuit breaker has been suitably, calibrated, the opening 73 may be filled or closed by a washer 80, preferably formed of fibre glass or other suitable material, which is inserted into the casing part 36 to close the said opening therein. Thereafter, any suitable sealing compound 82 may be inserted into the opening in the casing part 36 to seal the washer in position.

Referring now to Figure 3 in detail, there is illustrated a modification of the spindle 48 which serves as the combined pivot and calibrating element of Figs. 1 and 2. The spindle 48A of Fig.3 is substantially of the type fully illustrated and described in Patent No. 2,642,509 being provided with the slotted head 50A, the intermediate axially tapered and threaded operating portion 84, and the end bearing portions 86 and 88 which have rotary bearing support in complementary bearings 89 and 91 defined by the casing portions and 92, respectively. The combined pivot and calibrating member 48A is disposed within the threaded pivot aperture 40 of the movable contact member 10 and it will be apparent that when rotated in a direction to efifect the movement thereof in the direction of the arrow 72, transversely of the plane of contact member, the portion 44 of the latter is displaced, as previously described, to calibrate the circuit breaker in a direction to reduce the current rating or current response thereof. Similarly, as described, upon rotation or operation of the combined member 48 in the opposite direction, so as to withdraw the latter from the movable contact member 10, the inherent resiliency of the movable contact member permits the latter to spring back to reduce the previously described displacement thereof, so as to eiiect calibration in an opposite direction or sense, namely in a direction to increase the current rating or response of the circuit breaker. It will be noted that the casing portions 90 and 92, retain the movable contact member against lateral displacement when the spindle 48A is rotated therein.

Referring now to Figs. 4 and 5 in detail, there is illustrated another embodiment of the present invention, pursuant to which provision is made for a separate pivot member for the movable contact member and for a separate calibrating element therefor. More specifically, the general construction and arrangement is of the type illustrated and described in Patent 2,647,186 wherein the movable contact member 10A is provided with a pivot 94 which is suitably mounted in opposed bearing apertures 95 provided in the casing members 34 and 36, respectively. The movable contact member is provided with a generally circular peripherally interrupted tapered and threaded aperture 96 and a tapered threaded pin or calibrating member 98 for calibrating the circuit breaker. Said aperture is formed in the marginal edge of said movable contact member at the narrower portion 44 thereof which mounts the actuator 16. The calibrating member 98 is provided with a slotted head 100 and it will be understood that as the member 98 is threaded into the contact member 10, transversely of the plane thereof, in the direction of the arrow 72, the portion 44 of the movable contact member is displaced, as previously described in connection with Figs. 1, 2 and 3, to calibrate the circuit breaker for decreasing the current rating or response thereof by decreasing the degree or extent of overlap of the actuator tip 74 and the free end 20 of the bimetallic control element. In the present embodiment, the contact member 10A is also formed of a suitable material which has a required degree of inherent resiliency, as previously described. Therefore, as the calibrating member 98 is rotated in the opposite direction, to withdraw the latter from the contact member 10A, the inherent resiliency of the contact member will cause the latter to spring back to effect calibration in the opposite direction. It will be apparent that member 98 is withdrawn sufiiciently only to provide the required calibration in the opposite direction. It will be noted that the casing member 36 is apertured, as at 102, so that the required calibration in opposite senses, if necessary, may be effected without removing the circuit breaker mechanism from the casing, as previously described. A suitable washer 80 and sealing material 82 may be provided, as previously described, to seal the casing opening after the calibration is effected.

In each of the previously described embodiments, the calibration in opposite senses was effected by moving the tip 74 of the actuator relative to the free end 20 of the bimetallic control member 18. Referring now to Figs. 6 and 7 in detail, there is illustrated another embodiment of the invention pursuant to which calibration is etiected by movement of the bimetallic element 18 relative to the actuator 16. More specifically, there is illustrated a movable contact member construction substantially of the type illustrated in Patent No. 2,209,319. Pursuant to the present embodiment, the contact member 10B is provided with a longitudinal slot 104 therein which slot is adjacent the marginal edge 106 in the wider body part 46 of the contact member, and adjacent the point of attachment of the bimetallic element 13 to said marginal edge. The slot 104 is preferably closed at both ends but this is not essential. The slot provides an edge portion of the contact member, as described in said latter patent, which is readily distortable or displaceable in the direction of the arrow 108, and which when displaced serves to move the bimetallic element 18 so as to change its relationship with respect to the main body of the contact member and with respect to the actuator 16. In order to efiect displacement of the aforementioned displaceable edge portion of the contact member to which the actuator 18 is secured and which edge portion underlies the slot 104, provision is made for a threaded aperture 110 which is so positioned as to be intercepted by the slot 104. A tapered screw 112 is threaded into this aperture and it will be apparent that when the screw is turned and forced into the aperture so that the screw moves transversely of the plane of the contact member 10B, in the direction of the arrow 114 in Fig. 7, it will displace the edge portion of the contact member adjacent the slot. For example, the edge portion may be displaced in the direction of the arrow 108, and as illustrated in Fig. 10 in said latter patent. Said displacement of the edge portion of the contact member will move the bimetallic latch or control element 18 in said direction as indicated by the arrow 10S and also as illustrated in Fig. 10 of said latter patent. This results in the movement of the free end 20 of the bimetallic member in a direction so that said free end is overlapped to a lesser extent by the tip 74 of the actuator, whereby to decrease the current rating or current response of the circuit breaker. It will be understood that the contact member 10B is formed of a suitable material which has a required inherent resiliency, as previously described. Consequently, if it is desired to calibrate in the opposite direction, to compensate for overcalibration in the direction of the arrow 108, it will be apparent that the calibration screw 112 need only be rotated in an opposite direction to withdraw and move the latter transversely of the actuator 108, for a required extent, in a direction opposite the arrow 114. This results in a springback of the displaced edge portion 166 in a direction opposite the arrow 108 so as to move the latch end 20 in the opposite direction, for a required amount, to calibrate in the opposite direction. As in the various other embodiments, the casing member 36 is suitably apertured at 102 so that the calibration in opposite directions may be accomplished without removing the circuit breaker mechanism from the casing and the aperture may then be sealed by the washer 89 and the sealing means 82. The operation of the circuit breaker is described in detail in the previously mentioned patents and especially in Patent Nos. 2,647,186 and 2,209,319. However, it will be understood that the bimetallic element 18 operates to latch the manually operable actuator 16 to the movable contact member 10, 10A or 103, as the case may be, and to unlatch said actuator from the movable contact member, the unlatching taking place upon the deflection of the bimetallic element 18 causing the disengagement of the free end 20 thereof from the bottom part or tip 74 of the actuator 16 upon the occurrence of'an overload, or under other abnormal predetermined current conditionsrin the circuit controlled by the circuit breaker. When the bimetallic element 18, is deflected from engagement with the actuator 16, spring 24 is effective to move the contact member to its open position as illustrated, for example, in Fig. 4 of said Patent 2,647,186, wherein the contact 12 is disengaged from the, companion stationary contact 14.. In each of the described embodiments, the movable contact member is also provided with an electromagnetic member 116 to efiect instantaneous tripping of the circuit breaker on severe shorts or dangerous overloads. However it will be understood that said magnetic/tripping action is not essential to the, practice of the. present invention and therefore further description thereof is considered unnecessary and in this connection, it'will be understood that the magnetic tripping. operation is substantially of the-type described in Patent No. Re. 23,188 which is assigned to the assignee. of the present invention.

In view of the foregoing, it will be apparent, that pursuant to the present invention, provision is made for calibrating a circuit breaker mechanism in opposite directions or senses, so as to compensate or neutralize for overcalibration in one of said senses or durations, and that this may be accomplished both in the case where the actuator is adjusted relative to the control member or where the latter is adjustedrelative to the actuator.

While I have shown and described the preferred embodiments of my invention, it will be understood that various changes may be made in the present invention without departing from the underlying idea or principles of the invention within the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent, is:

1. In an automatic circuit breaker, a movable contact member, an actuator movably mounted on said member, a current-responsive control device including currentresponsive means releasably connected to said actuator for relea-sably latching said actuator to said movable member, means operable in a. first direction to adjust the shape of. said member and thereby adjust said releasable connection in a first direction for calibrating said circuit breaker in a first sense, and said member having sufiicient resiliency to provide adjustment of saidreleasable connection in an opposite direction in response to operation of said adjusting means in an opposite direction, whereby to eifect calibration of said breaker in an oppositesense.

2. In an. automatic circuit breaker, a movable contact member, an actuator movably mounted on said member, a current-responsive control device including current-responsive means releasably connected to said actuator for releasably latching said actuator to said movable member, a calibrating member, said calibrating member and said contact member having interengaging relatively adjustable parts for adjusting the shape of said member and thereby to adjust said releasable connection in a first direction upon operation of said calibrating. member in a first direction for calibrating said circut breaker in a first sense, and said contact member having inherent resiliency to provide adjustment of said releasable connection in an opposite direction in response to operation of said caiibrating member in an opposite direction, whereby to efiect calibration of said breaker in an opposite sense.

3. In an automatic circuit breaker, a movable contact member, an actuator movably mounted on said member, a current-responsive control device including currentresponsive means rele'asabiy connected to said actuator for releasably latching said actuator to said movable member, a calibrating member, said calibrating member and said contact member having interengaging relatively adjustable parts for adjusting the member and thereby to adjust said releasable connection in a first direction upon operation of said calibrating member in a first direction for calibrating said circuit breaker in a first sense, and said contact member having inherent resiliency to provide adjustment of said releasable connection in an opposite direction in response to operation of said calibrating member in an opposite direction, whereby to effect calibration of said breaker in an opposite sense, said calibrating member constituting pivot means on which said movable contact is mounted for pivotal movement.

4. In an automatic circuit breaker, a movable contact member, an actuator movably mounted on said memher, a current-responsive control device including currentresponsive means releasably connected to said actuator for releasably latching said actuator to said movable member, a calibrating member, said calibrating member and said contact member having interengaging relatively adjustable parts for adjusting the shape of said member and thereby to adjust said releasable connection in a first direction upon operation of said calibrating memher in a first direction for calibrating said circuit breaker in a first sense, and said contact member having inherent resiliency to provide adjustment of said releasable connection'in an opposite direction in response to operation of said calibrating member in an opposite direction, whereby to eflect calibration of said breaker in an opposite sense, and said contact member having means spaced from said calibrating member to mount said con-v tact member for pivotal movement.

5. In an automatic circuit breaker, a movable contact member, an actuating member carried on a part thereof, a current-responsive control device including ourrent-responsive means provided on another part of said contact member for operatively connecting said actuating member releasably to said movable contact for operating the latter except when said control device is disconnected from said actuating member upon overload, means operable in a first direction to relatively adjustably displace said parts in a first sense to calibrate the circuit breaker in a first direction, and said contact member being inherently resilient to provide relative adjustable displacement of said parts in an opposite sense in response to operation of said means in an opposite direction, whereby to calibrate the circuit breaker in an opposite direction.

6. In an automatic circuit breaker, a movable contact member, an actuating member carried on a part thereof, a current-responsive control device including currentresponsive means provided on another part of said contact member for operatively connecting said actuating member releasably to said movable contact for operating the. latter except when said control device is disconected from said actuating member upon overload, means operable in a first direction to relatively adjustably displace said parts in a first sense to calibrate the circuit breaker in a first direction, and said contact member being inherently resilient to provide relative adjustable displacement of said parts in an opposite sense in response to operation of said means in an opposite direction, whereby to calibrate the circuit breaker in an opposite direction, said displacing means being a tapered member engaged in an apertured portion of said contact member and operable transversely of said contact member in opposite directions.

7. In an automatic circuit breaker, a movable contact member, an actuating member carried on a part thereof, a current-responsive control device including currentresponsive means provided on another part of said con tact member for operatively connecting said actuating member releasably to said movable contact for operating the latter except when said control device isdisconnected from saidactuating member. upon overload, means operable in a first direction to relatively adjustably displace shape of said said parts in a first sense to calibrate the circuit breaker in a first direction, and said contact member being inherently resilient to provide relative adjustable displacement of said parts in an opposite sense in response to operation of said means in an opposite direction, whereby to calibrate the circuit breaker in an opposite direction, said displacing means being a tapered member engaged in an apertured portion of said contact member and operable transversely of said contact member in opposite directions, said apertured portion being disposed relative to said parts to efiect displacement of said first part relative to said other part.

8. An automatic circuit breaker comprising a casing having laterally spaced walls provided with aligned bearing portions, a movable contact member in said casing, pivot means for mounting said contact member in the casing for pivotal movement therein, an actuating member, means including a current-responsive device for operatively connecting said actuating member releasably to said contact member for actuating the latter, means including interengaging relatively adjustable parts of said pivot means and said movable contact member, respectively, for adjusting in a first direction the releasable connection between said actuating member and said current responsive device in response to operation of said last mentioned means in a first sense, and said movable contact member being formed of a resilient material for adjusting said releasable connection in an opposite di rection in response to operation of said last mentioned means in an opposite sense, whereby to calibrate the circuit breaker in opposite senses for automatic opening upon overload.

9. An automatic circuit breaker, as defined in claim 8, further characterized in that said pivot means includes a member which is internally screw threaded and which has a cylindrical portion turnably supported by one of said bearing portions, a spindle in which said movable contact member is mounted, one end portion of said spindle being in screw threaded engagement with said internally screw threaded member and the opposite end of said spindle being supported by the other of said bearing portions, said movable contact member having an opening therethrough, said opening extending to an edge of the contact member, and said spindle having an axially tapering part passing through said opening in engagement with the wall of said opening, whereby turning of said spindle in a first direction about its axis relatively to said movable contact member is effective to displace a part of the latter for adjusting in a first direction the releasable connection between said actuating member and said current responsive device to eifect said calibration in a first sense and turning of said spindle in an opposite direction effects a spring-back of said displaced part for adjusting said releasable connection in an opposite direction to effect said calibration in an opposite sense, and interengaging means in said internally screw threaded member and said movable contact member for retaining said members against relative rotation.

10. An automatic circuit breaker, as defined in claim 8, further characterized in that said pivot means comprises a spindle extending between said bearing portions and supported thereby, said movable contact member having an opening therethrough, said opening extending to an edge of the contact member, and said spindle having an axially tapering threaded part passing through said opening in threaded engagement with the wall of said opening, whereby turning of said spindle in a first direction about its axis relatively to said movable contact member is effective to displace a part of the latter for adjusting in a first direction the releasable connection between said actuating member and said current responsive device to elfect said calibration in a first sense and turning of said spindle in an opposite direction etfects a spring-back of said displaced part for adjusting said releasable connection in an opposite direction to effect said calibration in an opposite sense.

11. An automatic circuit breaker comprising a casing, a movable contact member in said casing pivot means for mounting said contact member in the casing for pivotal movement therein, an actuator movably mounted on a part of said contact member, a current-responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator, said movable contact member being formed of resilient material and having a peripheral interruption at a marginal edge portion thereof between said pivot and said actuator, and an axially tapered member passing through said interruption in engagement with the wall thereof, whereby axial movement of said tapered member in a first direction effects displacement of said part to move said actuator in relation to said current-responsive device for adjusting in a predetermined direction the releasably engaged portions of said actuator and said current-responsive device to calibrate the breaker in a first sense and axial movement of said tapered member in an opposite direction efiects a spring back of the displaced part to adjust said releasably engaged portion in an opposite direction to calibrate the breaker in an opposite sense.

12. In an automatic circuit breaker, a movable contact member formed of resilient material, an actuator device movably mounted thereon, a current-responsive control device carried by said member and having a free end in releasable engagement with said actuator to latch and unlatch said member thereto, said devices being provided on spaced portions of said member, an opening defined in said member, and a tapered member passing through said opening in engagement with the wall of said opening, whereby axial movement of said tapered member in a predetermined direction effects relative displacement of said portions for moving one of said devices relative to the other of said devices to adjust said releasable engagement for calibrating the circuit breaker in a pre determined sense and axial movement of said tapered member in the opposite direction effects a relative springback of said portions for calibrating the circuit breaker in an opposite sense.

13. A circuit breaker, as defined in claim 12, further characterized in that said tapered member pivotally mounts said contact member.

14. A circuit breaker, as defined in claim 12, further characterized in that said movable contact member is provided with a pivot between said spaced portions thereof and said opening is defined therein between said pivot and said actuator device, whereby the latter is adjustable relative to said control device.

15. A circuit breaker, as defined in claim 12, further characterized in that said movable contact member is provided with a pivot between said spaced portions thereof and said opening is defined therein between said pivot and said control device, whereby the latter is adjustable relative to said actuator device.

16. A circuit breaker, as defined in claim 12, further characterized in that the portion which carries said control device has a longitudinal slot near one edge which is closed at its ends and Which provides a readily displaceable edge portion to which said control device is secured, said slot intersecting said opening, movement of said tapered member in said predetermined direction effecting displacement of said edge portion to adjust the control device relative to the actuator device and opposite movement of said tapered member effecting a spring back of the displaced edge portion.

17. In an automatic circuit breaker, a movable contact member and a companion contact, means tending to drive said contacts apart and means holding said contacts together, said last-named means including a latching linkage and a current-deflected detent, said linkage including a member of resilient material and having an adjusting element engageable with relatively adjustable portions of said resilient member adjustable in one sense to establish the relative positions of said portions and thereby to establish a given extent of latching and in such adjustment increasing the resilient strain of said member, said element being adjustable in the opposite sense to establish different relative positions of said portions and thereby to establish a diiferent extent of latching and permitting reduction of the resilient strain in said member.

7 18. In an automatic circuit breaker, a movable contact member and a companion contact, means tending to drive said contacts apart and means holding said contacts together, said last-named means including a latching linkage and a current-deflected detent, said linkage including a member of resilient material and having a tapered adjusting element interposed between separate 12. integral parts of the member adjustable in one sense to establish a given extent of latching and in such adjustment increasing the resilient strain of said member, said element being adjustable in the opposite sense to establish a different extent of latching and permitting reduction of the resilient strain in said member.

References Cited in the file of this patent UNITED STATES PATENTS 2,065,357 Von Hoorn Dec. 22, 1936 2,195,016 Swingle Mar. 26, 1940 2,209,351 Sachs July 30, 1940 2,642,509 Cole et a1. June 16, 1953 2,647,187 Cole July 28, 1953 2,681,396 Cole et a1. June 15, 1954 

